1. Technical Field
The following description relates to a stereoscopic image display device and a method of driving the same, which capable of implementing a stereoscopic image (hereinafter, referred to as a “three-dimensional (3D) image”).
2. Discussion of the Related Art
The stereoscopic image display device can selectively implement not only a two-dimensional (2D) image, but also a three-dimensional (3D) image aided by development of various contents and circuit technique. The stereoscopic image display device implements the 3D image using a stereoscopic technique or an autostereoscopic technique.
Generally, the stereoscopic technique, which uses a binocular disparity between left and right eyes of a viewer, includes a glass method and a non-glass method. In the non-glass method, an optical plate such as parallax barrier or a lenticular lens is placed in the front or rear of a display screen. The glass method implements the 3D image by displaying a left eye image and a right eye image of which polarization directions are different from each other on a display panel and viewing the left and right eye images through polarization glasses or liquid crystal shutter glasses.
The liquid crystal shutter glasses method implements the 3D image by alternately displaying a left eye image and a right eye image on the display panel in a unit of frame, and opening or closing a left eye shutter or a right eye shutter of the liquid crystal shutter glasses in synchronized with a displaying timing. The liquid crystal shutter glasses make the binocular disparity in time-divisional driving method by opening only the left eye shutter during an odd-numbered frame period when the left eye image is displayed and opening only the right eye shutter during an even-numbered frame period when the right eye image is displayed. In the liquid crystal shutter glasses method, a luminance of the 3D image is low because the data on time of the liquid crystal shutter glasses is short, and 3D crosstalk is generated according to synchronization of the display panel and the liquid crystal shutter glasses, and on/off changing response characteristic.
The polarization glasses method uses a patterned retarder 2 attached on a display panel 1 as shown in FIG. 1. The polarization glasses method can implement a 3D image by spatially dividing left eye image and right eye image. For this, the polarization glasses method alternately displays the left eye image data L and right eye image data R on the display panel 1 in a unit of a horizontal line, and switches light input to the polarization glasses 3 having left and right lenses via the patterned retarder 2.
The stereoscopic display device according to the polarization glasses method includes a 3D formatter for processing 3D image signal from an external video source device such that the 3D image signal may be appropriately displayed on the display panel. The 3D formatter generates display data to be displayed on the display panel by separating the 3D image signal from the video source device into left eye image data L and right eye image data R, and alternately arranging the separated left eye image data L and right eye image data R in a unit of one horizontal line as shown in FIG. 2. Herein, the 3D image is input from the video source device to the 3D formatter in side by side type, top and down type, line by line type, and so on.
If the display panel is driven with the same frequency as the input frame frequency (e.g., 60 Hz) of the 3D image signal, the stereoscopic display device according to the polarization glasses method may include only the 3D formatter as shown in FIG. 3A. However, if the display panel is driven with a frequency (e.g., 120 Hz, 240 Hz, etc.) faster than the input frame frequency (e.g., 60 Hz) of 3D image signal, the stereoscopic display device according to the polarization glasses method may include a frame rate control (FRC) processor as well as the 3D formatter as shown in FIG. 3B. The FRC processor twice-copies the data from the 3D formatter in a unit of one frame to generate a display data to be displayed on the display panel if the display panel is driven with a double-speed frame frequency (120 Hz) which is twice faster than the input frame frequency (60 Hz). The FRC processor also quarter-copies the data from the 3D formatter in one frame unit to generate a display data to be displayed if the display panel is driven with a quad-speed frame frequency (120 Hz) which is four times faster than the input frame frequency (60 Hz).
However, there are some problems in the related art stereoscopic display device according to the polarization glasses method.
First of all, the related art stereoscopic display device alternately displays the left eye image data L and the right eye image data R on the display panel in a unit of one horizontal line. According to the spatial-divisional type, a display luminance displayed on the display panel by the left eye image data L is affected by the right eye image data R which is displayed neighboring to the left eye image data L on the display panel. Also, a display luminance displayed on the display panel by the right eye image data R is affected by the left eye image data L which is displayed neighboring to the right eye image data R on the display panel. Thus, there is a luminance deviation between the left eye image data L due to the display luminance of the neighboring right eye image data R. Further, there is a luminance deviation between the right eye image data R due to the display luminance of the neighboring left eye image data L.
For example, if a left eye image data L1 and a right eye image data R1 neighbored to each other have a same luminance as shown in FIG. 4, the right eye image data R1 following the left eye image data L1 has a first luminance (relatively bright luminance) because a charge delay of the right eye image data R1 is small. On the other hand, if a left eye image data L2 and a right eye image data R2 neighbored to each other have a different luminance as shown in FIG. 4, the right eye image data R2 following the left eye image data L2 has a second luminance (relatively dark luminance) lower than the first luminance because the charge delay of the right eye image data R2 is large. In spite of the luminance of the right eye image data R1 being the same as the luminance of the right eye image data R2, they are different from each other due to the display luminance of the left eye image data L1 and L2 which are neighbored to the right eye image data R1 and R2, respectively. This pattern holds for left eye image data L3, L4, L5, L6, etc. and right eye image data R3, R4, R5, R6, etc.
The luminance deviation between the left eye image data L is caused by the right eye image data R which are neighbored thereto, and the luminance deviation between the right eye image data R is caused by the left eye image data L which are neighbored thereto. The luminance deviation by the interference of the left eye image data L and the right eye image data R is perceived by viewers as a 3D crosstalk. The 3D crosstalk increases in proportional to the speed of the frame frequency. That is, the 3D crosstalk increases when the stereoscopic image device is driven with the double-speed frame frequency (120 Hz) rather when the stereoscopic image device is driven with the input frame frequency (60 Hz). Similarly, the 3D crosstalk increases when the stereoscopic image device is driven with the quad-speed frame frequency (240 Hz) rather when the stereoscopic image device is driven with the double-speed frame frequency (120 Hz).
Secondly, if there is a difference between a frame rate of display image and a perceiving ability of eye, motion blurring or ghost phenomenon is caused to decrease display definition of the stereoscopic image device. To prevent the decrease of display definition, application of a motion estimation motion compensation (MEMC) technique to a 2D image is proposed. The MEMC technique inserts at least one interpolation frame between the input frames to reduce the difference between the frame rate of display image and the perceiving ability of eye.
To apply the MEMC technique, it is necessary for the left eye image data L and right eye image data R to be separated from each other without being mixed. According to the related art polarization glasses type stereoscopic image display, it is difficult to process the signal from the 3D formatter using the MEMC technique because the left eye image data L and the right eye image data R are mixed to each other in a unit of one horizontal line in one frame display data generated by the 3D formatter. To apply the MEMC technique to the related art polarization glasses type stereoscopic image display apply the MEMC technique, it is necessary to use a very complicated signal process procedure. That is, to apply the MEMC technique to the related art polarization glasses type stereoscopic image display before the display data is generated, it is necessary to insert an interpolation frame through the MEMC technique and generate the display data in line by line type. Furthermore, to apply the MEMC technique to the related art polarization glasses type stereoscopic image display after the display data is generated, it is necessary to re-separate the display data generated in line by line type into left eye image data and right eye image data, insert the interpolation frame through the MEMC technique, and then re-generate the display data in line by line type.